1. Technical Field
The present invention relates to an atomic cell, a quantum interference device, an atomic oscillator, an electronic device, and a moving object.
2. Related Art
An atomic oscillator that oscillates based on energy transition of alkali metal atoms such as rubidium or cesium is known to maintain highly accurate oscillation characteristics for a long period of time.
Generally, an operation principle of the atomic oscillator is broadly classified into a technique of using a double resonance phenomenon caused by light and microwaves and a technique of using coherent population trapping (CPT) caused by two lights different wavelengths.
In an atomic oscillator using either one of the techniques, an alkali metal is generally enclosed in a gas cell (an atomic cell), and the gas cell is heated to a predetermined temperature by a heater so that the alkali metal is maintained in a certain gas state.
Here, generally, all of the alkali metal in the gas cell is not turned into gas, but rather a portion of the alkali metal becomes excess liquid. The excess alkali metal atoms become liquid by precipitation (condensation) in a portion of the gas cell having a low temperature. But, if the liquid alkali metal atoms exist in a portion through which excitation light passes, the liquid alkali metal atoms block the excitation light, and this causes a decrease of the oscillation characteristics of the atomic oscillator.
Therefore, in a gas cell disclosed in JP-A-2010-205875, a concave portion for precipitating alkali metal is provided on an interior wall surface of the gas cell.
However, in the gas cell disclosed in JP-A-2010-205875, the excess alkali metal precipitated in the concave portion is positioned relatively close to an area through which excitation light passes, and this state changes over time due to thermal diffusion and the like. Therefore, a portion of the excited gaseous alkali metal comes into contact with the excess alkali metal in the concave portion and a state of the excited gaseous alkali metal becomes uneven. As a result, the oscillation characteristics decrease (for example, a frequency change occurs).